1. Field of the Invention
The present invention relates to a probe cover, and more particularly, to a disposable probe cover for the probe of a tympanic thermometer.
2. Description of the Prior Art
Clinical thermometers are very helpful in the diagnosis of disease. The temperature of the tympanic membrane is generally considered to be superior to either oral, rectal or other auxiliary location for taking a patient's temperature because the tympanic membrane is more representative of the body's internal or core temperature. Temperature of the tympanic membrane can be measured by sensing infrared emissions emitted therefrom in the external ear canal. Besides, the infrared thermometers need less time when taking the patient's temperature reading. Therefore, the tympanic infrared thermometers have become more popular recently.
As seen in FIG. 1, in order to sense the infrared emissions in the ear canal, an elongated probe 11 must be partially inserted into the external ear canal. The infrared light emitted from the tympanic membrane passes through the window 12 at the distal opening 13 of the probe 11 and then is directed to the sensor of a thermometer by a waveguide (not shown). However, using such thermometers to measure the body's temperature of different patients raises a significant risk of contamination and spreading of disease. To preclude this risk, probes of such thermometers are protected with hygienic probe covers that are disposed of after each use. In addition to the sanitary barrier function, the probe covers should also fulfill the following additional functions. First, the probe cover must typically be transparent to light and having a wavelength in the far infrared range, or at least part of the probe cover must function as an infrared window. Also, the probe cover should provide for the easy and comfortable insertion of the probe into the ear canal.
Several devices have been suggested to accomplish these purposes. For example, a disposable speculum is disclosed in U.S. Pat. No. 4,662,360 to O'Hara et al. which includes a relatively rigid tubular body portion 22 and an infrared transparent membrane 21 attached to and sealing the distal end of the tubular body portion 22. The infrared transparent membrane 21 serving as the infrared window is made of polypropylene or polyethylene film that have a thickness in the range of 0.0005 to 0.001 inches. As seen in FIG. 2, the membrane 21 attaches to the outside of the distal end of tubular body portion 22, and a seam 23 is formed along the boundary. This seam 23 can be uncomfortable to patients if it protrudes excessively from the probe cover. On the other hand, the membrane may even fall into the ear canal if it is not securely attached.
Referring to FIG. 3, U.S. Pat. No. 5,163,418 to Fraden et al, there is disclosed a speculum probe cover which has a pleated sheath 33 to fit over the thermometer probe. The sheath is made from a single unitary piece of substantially infrared transparent film (approximately 0.001 inch thick) and the closed end of the sheath establishes an infrared window area 31. The periphery of pleated sheath 33 is attached to a ring shaped base 32 which is dimensioned to fit with the thermometer probe. Engagement of the base 32 of the probe cover onto the probe positions the infrared window area 31 across the path of infrared emission emitted from the tympanum. However, the pleats of the probe cover make the patients uncomfortable and the sheath itself makes a loud noise when being inserted into the ear canal. Besides, the infrared window area 31 may be ripped when the probe cover is applied onto the probe, which causes stray radiation of infrared emission that affects the accuracy of measured temperature.
Another probe cover is disclosed in U.S. Pat. No. 5,088,834 to Howe et al. Referring now to FIG. 4, a unitary probe cover includes a frustum-shaped sheath 43 which fits over the probe and a base 42 which is formed integrally with and extends around the periphery of the proximal end of the sheath 43 to hold the sheath over the probe. The sheath 43 is made of an infrared transparent material and is formed to have a thinner distal end portion terminating in a thin window 41 which has a thickness between 0.001 to 0.0005 inches and passes infrared radiation through the probe into the thermometer. Since the thickness of the wall of the sheath 43 is gradually reduced from 0.030 inch to 0.0005 inch, the thickness of the window 41 may vary after aging of the fabricating equipment. A thicker window can reduce the transparency to infrared emission while a thinner window may be easily broken. Also, a ripped window 41 may cause stray radiation of infrared emission that affects the accuracy of the measured temperature.